Limit number of reported known xids to avoid too many KnownAssignedXids error

test_runner/regress/test_replication_start_subxid_overflow.py

@@ -0,0 +1,43 @@
+from fixtures.log_helper import log
+from fixtures.neon_fixtures import NeonEnv, wait_replica_caughtup
+
+
+def test_replication_start_subxid_overflow(neon_simple_env: NeonEnv):
+    env = neon_simple_env
+
+    with env.endpoints.create_start(branch_name="main", endpoint_id="primary") as primary:
+        with primary.connect() as p_con:
+            with p_con.cursor() as p_cur:
+                p_cur.execute("begin")
+                p_cur.execute("create table t(pk serial primary key, payload integer)")
+                p_cur.execute(
+                    """create or replace function create_subxacts(n integer) returns void as $$
+                    declare
+                        i integer;
+                    begin
+                       for i in 1..n loop
+                          begin
+                              insert into t (payload) values (0);
+                          exception
+                              when others then
+                                  raise exception 'caught something';
+                          end;
+                       end loop;
+                   end; $$ language plpgsql""")
+                p_cur.execute("select create_subxacts(100000)")
+                xid = p_cur.fetchall()[0][0]
+                log.info(f"Master transaction {xid}")
+                with env.endpoints.new_replica_start(
+                    origin=primary, endpoint_id="secondary"
+                ) as secondary:
+                    wait_replica_caughtup(primary, secondary)
+                    with secondary.connect() as s_con:
+                        with s_con.cursor() as s_cur:
+                            # Enforce setting hint bits for pg_class tuples.
+                            # If master's transaction is not marked as in-progress in MVCC snapshot,
+                            # then XMIN_INVALID hint bit will be set for table's 't' tuple makeing it invisible.
+                            s_cur.execute("select * from pg_class")
+                            p_cur.execute("commit")
+                            wait_replica_caughtup(primary, secondary)
+                            s_cur.execute("select * from t where pk = 1")
+                            assert s_cur.fetchone() == (1, 0)